| Lowest Earned Run Average in Season | |||||||
| Updated 7/19/2005 | |||||||
| Rank | Year | Gms | IP | ER | ERA | ||
| 1 | 1967 | 32 | 259.66 | 61 | 2.114 | ||
| 2 | 1968 | 38 | 292.00 | 70 | 2.158 | ||
| 3 | 1979 | 44 | 366.00 | 106 | 2.607 | ||
| 4 | 1969 | 42 | 344.00 | 104 | 2.721 | ||
| 5 | 2005 | 58 | 491.66 | 151 | 2.760 | ||
| 6 | 1963 | 25 | 185.00 | 59 | 2.870 | ||
| 7 | 1972 | 33 | 273.34 | 92 | 3.029 | ||
| 8 | 1978 | 47 | 371.33 | 136 | 3.296 | ||
| 9 | 1982 | 37 | 299.98 | 112 | 3.360 | ||
| 10 | 1973 | 34 | 285.99 | 108 | 3.399 | ||
| 11 | 1999 | 51 | 425.67 | 164 | 3.467 | ||
| 12 | 2003 | 58 | 491.67 | 193 | 3.533 | ||
| 13 | 1980 | 43 | 361.68 | 147 | 3.658 | ||
| 14 | 2004 | 48 | 406.67 | 175 | 3.873 | ||
| 15 | 1974 | 30 | 240.00 | 106 | 3.975 | ||
| 16 | 1966 | 30 | 226.00 | 106 | 4.221 | ||